The 3" RT Spacer allows changing back-focus by providing quick connect/disconnect spacing of the 3" RT Steeltrack Focuser (39mm spacing length).
- 4" external dovetail on one side for attachment of 3" RT Steeltrack Focuser.
- 4" internal dovetail receiver on opposite side, with 3 lock screws.
- 39mm spacing length.
- Baffled and blackened internal surface kills off-axis stray light.